With the advance of solid state electronics, various improved means of dissipating the heat generated by solid state components have been investigated. The standard forced air convection means appears to have reached its limit of practicality in that the amount of air that is required to provide sufficient cooling for the limited heat dissipating surfaces introduces a noise problem, and without some auxiliary techniques cannot maintain each of a large number of components, such as integrated circuit semiconductor chips, within their proper operating temperature range. Accordingly, especially in connection with high speed data processing systems and the like, combinations of air-liquid cooling systems have been devised. One such system is an immersion cooling system, wherein the array of components to be cooled is immersed in a tank of cooling liquid. The liquids frequently employed are the fluorocarbon liquids which have a low-boiling point. These liquids are dielectric and give rise to various types of boiling at relatively low temperatures. In view of the problems encountered in servicing and packaging components which are cooled using this immersion technique, an encapsulated cooling technique was provided which includes the same dielectric material encapsulated separately for each module. U.S. Pat. No. 3,741,292, issued June 26, 1973 shows an example of a module having the heat generating components located thereon surrounded by a low boiling point dielectric liquid which is encapsulated thereto. A vapor space is located above the liquid level, which is filled with internal fins extending into the container serving as a condenser for the dielectric liquid vapors. External fins extend outward from the container and serve as an air cooled sink for the internal fins condenser. However, this type of a modular liquid encapsulated cooling device must meet certain inflexible requirements. For instance, it requires coolant of extremely high purity and free of any contaminants. It's operation is sensitive to all the variables which govern the basic process of nucleate boiling and vapor condensation. Furthermore, the concept is not readily adaptable to small scale applications such as a single heat generating component or semiconductor chip.
Reference is made to U.S. Pat. No. 3,993,123 entitled "Gas Encapsulated Cooling Module" granted Nov. 23, 1976 to Richard C. Chu et al. In the Chu et al. Patent a gas encapsulated cooling unit is provided for one or more heat generating devices (such as semiconductor chips) to be cooled. The components are mounted on a substrate. A cap is sealed to the substrate enclosing the heat generating devices to be cooled. An inert gas and good thermal conductive elements are contained within the sealed volume between the cap and the substrate. Each of the heat conductive elements are urged against respective ones of the heat generating devices forming a small gas gap (interface) to provide low thermal resistance. A heat sink associated with the cap receives the heat from the heat conductive elements through an annular gap which likewise contains inert gas.
Reference is made to U.S. Pat. No. 3,512,582 entitled "Immersion Cooling System for Modularly Packaged Components" granted May 19, 1970 to Richard C. Chu et al. In the Chu et al patent an immersion cooling system for modularly packaged components (such as semiconductor chips) is provided comprising a common vessel containing a low-boiling-point liquid. A plurality of modular units, each containing an individual cooling chamber, are connected to the common vessel by respective input and output conduit means. The individual cooling chambers and the input conduit means are arranged with respect to the common vessel such that the liquid will flow from the vessel through the input conduit into the individual cooling chambers by gravitational force. The output conduit means provides the vent path and liquid expansion path for the respective cooling chambers. Heat generating components are located in each of the cooling chambers in heat exchange contact with the low boiling-point liquid so as to provide cooling. A heat exchanger is provided associated with each of the individual cooling chambers for removing heat from the low-boiling point liquid so as to provide sufficient cooling to maintain said electronic components substantially at a predetermined temperature.
Reference is made to U.S. Pat. No. 3,524,497 entitled "Heat Transfer In A Liquid Cooling System" granted Aug. 18, 1970 to Richard C. Chu et al. In the Chu et al patent electronic components, such as semiconductor chips, or the like, are mounted on one end of heat conducting cooling studs. The semiconductor carrying ends of the cooling studs are connected to one side of a circuit board. The circuit board forms one wall of a narrow channel through which liquid is forced to flow. The studs extend from the wall into the channel in spaced relationship with respect to one another. Further studs, connected to the opposite wall, extend into the channel, parallel to the cooling studs and in spaced, staggered relation thereto. The further studs cause an increase in the turbulence of the flowing liquid around the heat conducting studs and direct the flow of cooling liquid over a greater area of the cooling studs, thus increasing the heat transfer therefrom.
Reference is made to U.S. Pat. No. 3,586,101, entitled "Cooling System for Data Processing Equipment" granted June 22, 1971 to Richard C. Chu et al. The Chu et al patent discloses a liquid cooling system for data processing equipment in which a plurality of electronic component modules to be cooled are located in chambers which have a cooling liquid circulating therethrough by gravity feed from a buffer storage reservoir located at the top of the cooling system. A phase-separation column is provided which is connected to the output of each of the module chambers by equal length conduits. The components within the modules give rise to nucleate boiling within the cooling liquid. The vapor bubbles and the cooling liquid passes through the conduit and enter the phase-separation column where the vapor bubbles rise and the liquid drops. A condenser is located above the phase-separation column for condensing the vapor bubbles. The condensate and the liquid in the phase-separation column are returned to the circulation system. A cooling means is located in the circulation system for returning the cooling fluid to a temperature below the boiling point.
Reference is made to U.S. Pat. No. 3,673,306 entitled "Fluid Heat Transfer Method and Apparatus for Semi-Conducting Devices" granted June 27, 1972 to Milton E. Kirkpatrick. The Kirkpatrick patent discloses the use of a heat pipe type thermal conductive path within a metallic housing such as a transistor can for cooling of high power semiconductor devices which normally require large heat dissipation. An electrically non-conductive wick structure is provided which is formed, for example, from high purity silica glass cloth in a shape resembling a hollow "marshmallow" and which forms a liner for the entire transistor can. The wick contacts both the active surface of the semiconductor device in the bottom of the can and the upper walls of the can. Prior to placing the can upon its mounting base, an appropriate amount of electrically non-conductive, non-polar working fluid such as high purity organic liquid is loaded so that it entirely fills or saturates only the wick like structure. The working fluid held within the wick is thus in immediate contact with the active surface of the semiconducting device. In operation, the surface of the semiconductor device serves as the evaporator section of the closed loop heat pipe. As fluid is caused to evaporate from this region, heat transfer and thus cooling of the device is effected. The vapor thus produced is recondensed over regions of the can which are at slightly cooler temperatures than the semiconductor device. The working fluid vapor thus provides an efficient heat transfer path to the entire radiating surface of the can in order to dissipate the thermal energy of concern.
Reference is made to U.S. Pat. No. 3,957,107 entitled "Thermal Switch" granted May 18, 1976 to Frank E. Altoz. The Altoz Patent discloses a sealed extensible bellows containing freon and a flexible wick providing a heat pipe. The fixed end of the bellows is attached to a heat sink (a cold body). The other movable end of the bellows carries a thermally conductive plate that moves from a non-engaging relationship to an engaging relationship with a temperature regulated surface (for example an oscillator circuit) at a predetermined temperature of the cold body.
Reference is made to the IBM Technical Disclosure Bulletin Publication entitled "Modular Heat Sink" by H. Parsapour, Vol. 17, No. 11, April 1975, page 3313. In the Parsapour publication heat conductivity and thermal contact between a heat sink and a semiconductor module is obtained by using a heat pipe in the form of a longitudinally flexible bellows tube.
Reference is made to the IBM Technical Disclosure Bulleting Publication entitled "Controlling Pressure Changes in a Liquid Encapsulated Module" by N. G. Aakalu et al, Vol. 14, No. 8, January 1972, page 2533. In the Aakalu et al publication the pressure change is compensated for by a bellows which is completely immersed within the liquid. The bellows has an opening to the ambient air for operation.